Change Constant::Binary back to refcount clone byte strings

[rschoon]

This changes the Constant type to be able to copy the shared reference to a byte string again.

This depends on rust-lang/rust#77560

changelog: none

[rust-highfive]

r? @phansch

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[ghost]

Is this pull request needed? I think the change should get synced from rust after that pull request is merged.

[ebroto]

@rschoon in case your PR to rust-lang/rust is accepted, the workflow is to sync back that commit to this repo like @mikerite suggests.

Take a look here for a description of the process. Anyone can do it, although the process is a bit cumbersome for now.

[rschoon]

I'll take a look. When I tried getting git-subtree working before (following the instructions in the rustc dev guide) I couldn't get it to work, but I didn't have the patched version of git-subtree.

[ebroto]

Thanks! In case of running into problems, don't hesitate to ping me or @flip1995, as we've done it before it would be easier for us because the first time it takes around 40 mins IIRC 😅